1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device that is mounted, for example, in face-down on a printed wiring board and more particularly to a manufacturing method of a semiconductor package that has an approximately identical size as a semiconductor chip.
2. Description of Related Art
When a semiconductor chip is mounted on a printed wiring board to constitute an electronic device, so called high density mounting is demanded to mount more semiconductor chip in a definite area. In order to realize this high density mounting, a CSP (Chip Scale Package or Chip Size Package) that has an approximately identical size as a semiconductor chip is developed.
However, when a CSP is manufactured, for each semiconductor chip that is cut out of a wafer, an assembling is required. Accordingly, there is a problem that manufacturing process becomes complicated.
To cope with such a problem, a method is proposed in which after assemblage of a device on a wafer, this semiconductor device is cut out of the wafer. For example, in Japanese Patent Laid-open Publication (KOKAI) No. Hei 9-172036, a manufacturing method of CSP that comprises a step of printing paste of conductor on a semiconductor chip to form a protruded electrode (bump), and a step of coating insulating material on a surface of the semiconductor chip other than on the protruded electrode to form a sealed body is disclosed.
In general, in order to mount a semiconductor device such as a CSP on a printed wiring board or the like, electrodes are formed on the wiring board corresponding to bumps of the semiconductor device, and the bumps are pushed to contact to this electrode pattern, and thereafter the pushed portions are heated and melted to connect.
A semiconductor chip and a printed wiring board being used for CSP are largely different in their values of thermal expansion coefficient. Accordingly, when heat during mounting or heat cycle during use is added, due to difference of the thermal expansion coefficient stress concentrates on joint portion of the bump. Thereby, the joint portion tends to peel or to be high in electrical resistance. Thermal stress that is generated at the joint portion of the bump, by raising a height of bump, can be alleviated.
However, in a method that is disclosed in Japanese Patent Laid-open Publication (KOKAI) No. Hei 9-172036, a height of bump can not be sufficiently raised. That is, in this method, paste of conductor is coated by the use of screen printing method on an electrode pad of a semiconductor chip to form a protruded electrode (bump). By a thickness of a mask (metallic mask) during screen-printing, the height of the bump is determined. In the case of metallic mask, a ratio of thickness to diameter of opening can not be made so large. Accordingly, a bump that is sufficiently high for alleviating thermal stress could not be formed.
In addition, in the aforementioned manufacturing method of CSP, on a surface of a semiconductor chip other than on the electrode portion, a film of curable resin is coated. Since thermal expansion coefficient of the film is larger than that of the semiconductor chip, during letting cool naturally the film after heat treatment, thermally shrinking force of the film is restricted by the semiconductor chip to generate thermal stress. As a result of this, the semiconductor device bends toward the film to induce disturbance in mounting on a printed wiring board or the like.